We report an unusual case involving a 70-year-old man with multiple coronary aneurysms, including a 5-cm aneurysm of the right coronary artery. The precise size was determined with magnetic resonance imaging, although the aneurysms were diagnosed initially on angiography. Multiple coronary aneurysms are rare in adults, The cause may have been atherosclerosis, syphilis, or collagen vascular disease, all of which cause weakening of the media. The patient underwent successful operation, including coronary artery bypass grafting.